Israel's prime minister is flying to Washington on what may prove to be a divisive visit.
Benjamin Netanyahu has been invited, by Republicans, to speak to lawmakers in Congress about Iran's nuclear programme.
President Obama - who has frosty relations with Mr Netanyahu - was not consulted about the trip, with Reuters saying plans were made public in an "apparent breach of protocol".
Earlier this week, Obama's national security adviser Susan Rice said the visit "injected a degree of partisanship, which is not only unfortunate, I think it’s destructive of the fabric of the relationship" between the US and Israel.
Mr Netanyahu told reporters before departing that "I’m going to Washington on a fateful, even historic, mission... I feel that I am an emissary of all Israel's citizens, even those who do not agree with me, and of the entire Jewish people."
Obama and Netanyahu have been divided over approaches to halting the Iranian nuclear programme, with the Israeli politician calling for a complete halt to the the programme. Obama is reportedly willing to allow a small amount of nuclear activity to continue, as long as there are assurances no weapons will be developed.
The US is currently leading talks with Iran on their programme.
Elections are set to take place in Israel later this month, where Mr Netanyahu will be looking to be re-elected.
